Streak Tube Imaging Lidar (STIL) is used for the imaging and detection of targets in a turbid medium such as water or air. In terms of imaging an underwater region, STIL uses a pulsed fan beam to illuminate a thin strip on the ocean bottom that corresponds to a single (cross-track) line in the rendered imagery. Photon returns of the ocean bottom and corresponding adjacent water column are captured in a CCD array, essentially capturing a thin volumetric slice, or shot of the ocean in terms of volumetric pixels or voxels as they are known. Each pixel can be represented by a temporal profile which contains an approximate Gaussian shaped curve of the bottom return.
The three-dimensional nature of STIL data yields large data files which require relatively large amounts of time to process and/or transmit. Accordingly, the three-dimensional STIL data is often rendered into two-dimensional forms thereof. In general, STIL data can be rendered into two-dimensional contrast and range maps by finding the peak value of the temporal profile of each pixel. The magnitude of the peak value corresponds to the contrast and the location of the peak value corresponds to the range.
Current methods of rendering involve searching the temporal profile for a matched Gaussian curve fit. However, this technique is limited in that the prior estimates of the Gaussian curve width must be known. That is, problems arise when the true width of the Gaussian curve in the temporal profile is different from the fitted width. In addition, prior to the Gaussian curve match fit, dark field and ambient light fields must be determined and removed from the temporal profile. The current methods use a separate dark field file to remove the dark field values and must estimate a Ksys value (i.e., a measure of how turbid the medium is in terms of how rapidly the STIL system's laser beam decays) to compute the ambient light field exponential decay curve. However, this means that a separate dark field file must be provided. Also, poor estimates of the Ksys value yield poor rendering results.